In a controlled experimental canine model the effect of histocompatibility matching at the D-La locus by use of serological tests and mixed lymphocyte culture upon the outcome of full thickness penetrating keratoplasty will be determined. Previous alkali burns will induce uniform vascularization in each host, insuring a poor prognosis situation. With vascularization the host graft bed will be exposed to normal immune processes. Each animal will be matched for and receive a penetrating keratoplasty in the vascularized eyes. Comparison of identical, highly compatible and highly incompatible matches will be made. Animals will be routinely tested for the production of lymphocytotoxic antibodies before and three months after transplantation. Serological cytotoxicity tests will be performed on each animal. An analysis and comparison of SD versus LD antigens and their effect on graft outcome will also be done.